Proteoglycan, a major constituent of cartilage matrix, has recently been shown to be comprised of a proteoglycan subunit linked non-covalently by hyaluronic acid and link proteins to form proteoglycan complexes. Our previous work has indicated that the immunogenicity of proteoglycan is due to the link proteins and at least two distinct antigens in the proteoglycan subunit core protein. We propose to isolate and characterize each of the components of proteoglycan and to prepare monospecific antisera for each component. These specific antisera will be used to study the distribution of proteoglycan components in cartilage slices and other tissues by immunofluorescence, to better visualize proteoglycan structure by electron microscopy, to help study proteoglycan synthesis, and to measure proteoglycan components in synovial fluid. The basis of the change in carbohydrate content of proteoglycan with age and of the apparent fragmentation of the proteoglycan subunit in osteoarthritis will be investigated. The organization and conformation of proteoglycan and its components will be studied by nuclear magnetic resonance spectroscopy. These studies will provide new information as to the structure and organization of proteoglycan in normal cartilage and help to clarify the nature and pathogenesis of the alterations occurring with age and arthritis. In human IgG immunoglobulin, biologic activity resides in the Fc fragment. It is this region which is responsible for 1) complement fixation and interaction with Clq; 2) attachment to cell membrane receptors; 3) placental transmission; and 4) reverse passive cutaneous anaphylaxis in the guinea pig. This research is intended to determine the structure of the active sites in the Fc region of IgG responsible for these biological activities. Four fragments of the Fc region of the four subclasses of IgG myeloma proteins will be made by cleavage with cyanogen brombide. Each fragment will be tested for the biologic activities described above, active fragments will be cleaved into peptides with proteolytic enzymes and the amino acid sequence of active peptides will be determined.